Export py_to_scalar

minarrow-py/src/lib.rs

@@ -48,7 +48,7 @@ pub use chunked_array::PyChunkedArray;
 #[cfg(feature = "ndarray")]
 pub use chunked_ndarray::{PyChunkedNdArray, PyChunkedNdArrayInner};
 pub use chunked_table::PyChunkedTable;
-pub use convert::{build_array, resolve_index, scalar_to_py};
+pub use convert::{build_array, py_to_scalar, resolve_index, scalar_to_py};
 pub use dtype::{dtype_from_arrow, width_from_arrow, DType, TypeClass};
 pub use field::{PyField, PySchema};
 #[cfg(feature = "ndarray")]

pyo3/src/ffi/to_py.rs

@@ -29,7 +29,7 @@ use minarrow::ffi::arrow_c_ffi::{
     export_super_table_view_stream, export_to_c, export_view_to_c, ArrowArray, ArrowArrayStream,
     ArrowSchema,
 };
-use minarrow::ffi::arrow_dtype::{ArrowType, CategoricalIndexType};
+use minarrow::ffi::arrow_dtype::ArrowType;
 #[cfg(feature = "datetime")]
 use minarrow::enums::time_units::TimeUnit;
 use minarrow::ffi::schema::Schema;
@@ -130,19 +130,7 @@ fn arrow_type_to_pyarrow<'py>(
         }
 
         ArrowType::Dictionary(key_type) => {
-            let index_ty = match key_type {
-                #[cfg(feature = "default_categorical_8")]
-                CategoricalIndexType::UInt8 => pa.call_method0("uint8")?,
-                #[cfg(feature = "extended_categorical")]
-                CategoricalIndexType::UInt16 => pa.call_method0("uint16")?,
-                #[cfg(any(
-                    not(feature = "default_categorical_8"),
-                    feature = "extended_categorical"
-                ))]
-                CategoricalIndexType::UInt32 => pa.call_method0("uint32")?,
-                #[cfg(feature = "extended_categorical")]
-                CategoricalIndexType::UInt64 => pa.call_method0("uint64")?,
-            };
+            let index_ty = pa.call_method0(key_type.arrow_index_name())?;
             let value_ty = pa.call_method0("utf8")?;
             pa.call_method1("dictionary", (index_ty, value_ty))
         }

src/ffi/arrow_dtype.rs

@@ -404,6 +404,31 @@ pub enum CategoricalIndexType {
     UInt64,
 }
 
+impl CategoricalIndexType {
+    /// The Arrow name of the integer type that carries the dictionary's keys,
+    /// as used by Arrow and PyArrow.
+    ///
+    /// The variants present in a build depend on the categorical width
+    /// features. A downstream crate reads the name here rather than matching on
+    /// the enum, because such a match compiles only while both crates select
+    /// the same widths.
+    pub fn arrow_index_name(&self) -> &'static str {
+        match self {
+            #[cfg(feature = "default_categorical_8")]
+            CategoricalIndexType::UInt8 => "uint8",
+            #[cfg(feature = "extended_categorical")]
+            CategoricalIndexType::UInt16 => "uint16",
+            #[cfg(any(
+                not(feature = "default_categorical_8"),
+                feature = "extended_categorical"
+            ))]
+            CategoricalIndexType::UInt32 => "uint32",
+            #[cfg(feature = "extended_categorical")]
+            CategoricalIndexType::UInt64 => "uint64",
+        }
+    }
+}
+
 // Design documentation: arrow_type()
 //
 // Whilst `arrow_type()` could be on a trait, the ergonomics of using one aren't great